Cows, rats, and mice are highly susceptible to urinary bladder carcinogenesis by bracken fern. Milk obtained from cows ingesting bracken fern contains toxic, mutagenic and carcinogenic metabolites not normally present in cow milk. Human ingesting bracken fern or such milk might be unwittingly exposed to a naturally-occurring plant carcinogen. Human consumption of this plant predisposes to an augmented risk to esophageal carcinoma. Tannin isolated from bracken fern is non-carcinogenic when given p.o., but was tumorigenic when administered s.c. or implanted intravesically. Carcinogenicity of bracken fern appears not to be associated with tannin when given orally, because tannin-free fractions of bracken fern are carcinogenic when fed rats. The urine of rats given tannin-free fraction of bracken fern contain mutagenic metabolites, not present in urine of rats fed tannin. Carcinogenic compound(s) in tannin-free fractions of bracken fern and carcinogenic metabolites in bracken fed cow milk will be identified and tested for carcinogenic activity utilizing rodents and microbiological system. The proposed studies are designed to meet the specific study objectives outlined in the Experimental Biology, Sunflow Phase II-1, 1-A, Phase II-2, 2-A and Phase II-2, 2-B of the National Bladder Cancer Project.